RD-253 -275 -276 engines
A full-scale demo version of the RD-253 engine.
The original first stage of the Proton rocket was propelled by six RD-253 engines developed at OKB-456 design bureau (now NPO Energomash) in Moscow and led by Valentin Glushko. Each engine had a thrust on the ground of 150 tons. Like the engines on two upper stages of the Proton rocket, RD-253 burned highly toxic unsymmetrical dimethylhydrazine as a fuel mixed with nitrogen tetroxide as an oxidizer.
On the first stage of the Proton rocket, RD-253 was installed in a movable suspension system that allowed to swivel each individual engine around a single axis. Combined movement of all six engines enabled the flight control system of the rocket to steer the vehicle along its prescribed trajectory.
In 1986, specifically for the launch of core module of the Mir space station, the thrust of RD-253 engine was increased by seven percent. It was achived thanks to a minor modification to the propellant flow control valves. Since then, engines incorporating this change have undergone extensive additional qualification firings, in order to approve them for use in standard production vehicles.
From 1987 to 1993, NPO Energomash developed a more powerful version of the engine, designated RD-275, which has been used on the first stage of the Proton rocket until 2007, when the improved RD-276 model was introduced. The engines are mass produced at PPO Motorostroitel (also known as Permskie Motory or PAO Proton-MP) in the city of Perm.
As late as 2017, Proton's first stage engines still used non-Russian components, most likely produced in Ukraine, and NPO Energomash promised to certify Russian-built replacements in 2018.
In September 2018, Acting Director at PAO Proton PM Dmitry Shenyatsky, quoted by RIA Novosti, said that four final RD-276 engines would be produced and tested by the company in the first quarter of 2019.
Specifications of RD-253 engine:
RD-253 engines during assembly. Credit: Proton PM
The 11D43 engine proposed by Valentin Glushko around 1960 for the first stage of the Proton rocket. It had low-expansion ratio and could be gimbaled to control the rocket in flight. Four such engines along with four 8D43 engines would be used on the first stage, if this configuration was ever built. Click to enlarge. Copyright © 2000, 2011 Anatoly Zak
A scale model of RD-253 engine. Copyright © 2001 Anatoly Zak
A business end of the Proton rocket with six RD-275 engines arranged in circle on the first stage. Click to enlarge. Copyright © 2000 Anatoly Zak
A test stand in the city of Perm used for live firings of RD-275 engines. Credit: Roskosmos